Abstract
Esterase, as a type of powerful catabolic enzyme for the degradation of pyrethroid pesticides (PYRs), appears promising in improving the quality of crops and the environment contaminated by pesticide residues. The purpose of this research is to provide a detailed introduction to the enzymatic properties, optimal production and immobilization conditions, and the degradation ability of Est804 for PYRs. The study on enzymatic properties indicated that Est804 was an alkaline esterase with an optimal pH of 8.0 and a broad optimal temperature in the range of 35-50°C. The optimal activity of free Est804 was calculated to be 112.812 U, and the specific enzyme activity was 48.97 U/mg. The kinetic parameters of Est804 were K m = 0.613 mM, k cat = 12,371 s-1, and V m = 0.095 mM/min. The results of the fermentative optimization demonstrated that the optimal conditions included 1.5% of inoculation amount, 30 mL of liquid volume, 28°C of the fermentation temperature, and 18 h of the fermentation time. The optimal medium consists of 15.87 g of yeast powder, 8.00 g of glycerol, and 9.57 g of tryptone in 1 L of liquid. The optimized enzyme activity was 1.68-fold higher than that before optimization. Immobilized Est804 exhibited the highest activity under the optimum preparation conditions, including 0.35 g of chitosan dosage, 0.4 mL of an enzyme, and 4 h at 40°C for adsorption. The degradation rates of Cypermethrin (CYP), fenpropathrin (FE), and lambda-cyhalothrin (LCT) by Est804 within 30 min were 77.35%, 84.73%, and 74.16%, respectively. The present study indicated that Est804 possesses great potential for the treatment of pesticide residues on crops and environmental remediation, conducive to the development of SGNH family esterase against pyrethroid accumulation.